8357653: Inner classes of type parameters emitted as raw types in signatures

[biboudis]

In the following example, G.Getter is erroneously treated as a raw type by javac:

static abstract class Getters<X> {
  abstract class Getter {
      abstract X get();
  }
}

static class Usage1<T, G extends Getters<T>> {
  public T test(G.Getter getter) {
      return getter.get();
  }
}

The (now reverted) #25346 attempted to fix this by skipping type variables in the calculation of allparams().

While that seemed to fix the type checking error, it was a fragile solution in a number of ways.

• allparams() is passed to a method that calculates substitutions. This signals that the method adheres to invariants during substitutions where lists of type parameters are expected to be of the same length (for the from and to parts). Affecting directly the allparams_field seems not the right approach.
• Another observation (thx @liach) was that in the generated bytecode, the fully qualified type of the inner class G still appeared as if it originated from a raw type. assembleClassSig independently examines outer to detect whether it is raw or not.
• Finally, there is already a proper area in javac, earlier in the pipeline, where javac handles/detects "rare types" (test/langtools/tools/javac/generics/rare): That method is checkId and specifically checkIdInternal. While in the general case the type of an identifier is the symbol's type, checkIdInternal computes a new type in two occasions. In one of those occasions, checkIdInternal is computing the type when the symbol's type is an inner class. Here, we can start normalizing (by skipping the type variables).

Moreover, it has been observed that asEnclosingSuper is a generalization of asOuterSuper and additionally the former is used only in checkIdInternal. As a result, this PR performs two simplifications:

As a first simplification this PR replaces asOuterSuper with asEnclosingSuper.
As a second simplification this PR relies only on the owner's enclClass() based on the following subsequent observations:

• An enclosingType() call returns the outer_field directly and Type.noType otherwise (in the case of an inner class it refers to the type of its enclosing instance class.)
• An enclClass() call returns the closest enclosing class and the behavior in asEnclosingSuper containing a loop with the condition t.hasTag(CLASS) combined with asSuper(t, sym) is believed to be the same.

The test now includes bytecode tests additionally to the reflection-based reproducer and the original test case.

// edit: this PR does not perform this simplification and retains asOuterSuper.

---

Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change requires CSR request JDK-8359213 to be approved
• Change must not contain extraneous whitespace
• Commit message must refer to an issue

Issues

• JDK-8357653: Inner classes of type parameters emitted as raw types in signatures (Bug - P4)
• JDK-8359213: Inner classes of type parameters emitted as raw types in signatures (CSR)

Reviewers

• Vicente Romero (@vicente-romero-oracle - Reviewer)
• Maurizio Cimadamore (@mcimadamore - Reviewer) Review applies to 6cec56aa

Contributors

• Maurizio Cimadamore <[email protected]>

Reviewing

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[bridgekeeper]

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[openjdk]

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[biboudis]

/csr needed

[openjdk]

@biboudis has indicated that a compatibility and specification (CSR) request is needed for this pull request.

@biboudis please create a CSR request for issue JDK-8357653 with the correct fix version. This pull request cannot be integrated until the CSR request is approved.

[biboudis]

/contributor add @mcimadamore

[openjdk]

@biboudis
Contributor Maurizio Cimadamore <[email protected]> successfully added.

[mlbridge]

Webrevs

• 02: Full - Incremental (68364b85)
• 01: Full - Incremental (6cec56aa)
• 00: Full (f33753bf)

[mcimadamore]

Looks good - I'm unsure whether we should unify the two routines as part of this fix, or if we wanna keep that for a separate PR (given that might be a potential extra risk)

[vicente-romero-oracle]

looks sensible to me

[vicente-romero-oracle]

looks good